Impedance matching for a dual band power amplifier

• US 6,243,566 B1
• Filed: 05/01/2000
• Issued: 06/05/2001
• Est. Priority Date: 02/19/1997
• Status: Expired due to Term

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Black, Gregory Redmond, Peckham, David Sutherland
• Primary Examiner(s): Eisenzopf, Reinhard
• Assistant Examiner(s): Bhattacharya, Sam
• Application Number:
  US09/562,734
• Time in Patent Office: 400 Days
• Field of Search: 455/93, 455/114, 455/115, 455/126, 455/127, 455/129, 455/341, 330/51, 330/286, 330/306, 330/279, 333/32, 333/33
• US Class Current: 455/127.4
• CPC Class Codes: H03F 1/56 Modifications of input or output impedances, not otherwise provided for
• CPC Class Codes: H04B 1/00 Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
• CPC Class Codes: H04B 1/005 adapting radio receivers, transmitters andtransceivers for operation on two or more bands, i.e. frequency ranges
• CPC Class Codes: H04B 1/04 Circuits
• CPC Class Codes: H04B 1/0458 Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages matching circuits in general H03H
• CPC Class Codes: H04B 1/406 with more than one transmission mode, e.g. analog and digital modes

Abstract

An exciter matching circuit (125), interstage matching circuit (134), and harmonic filter matching circuit (140) match impedances at the input to a two-stage power amplifier (130), between the first stage (132) and the second stage (136) of the power amplifier (130), and at the output of the power amplifier (130) for more than one frequency band of interest. In a GSM/DCS dual band radiotelephone (101), the matching circuits (124, 134, 140) provide low return loss at 900 MHz when the dual band transmitter (110) is operating in the GSM mode. The harmonic filter matching circuit (140) also filters out signals at 1800 MHz, 2700 MHz, and high order harmonics. When the dual band transmitter (110) is in DCS mode, however, the matching circuits (124, 134, 140) provide a low return loss at 1800 MHz and filter out signals at 2700 MHz and harmonics of 1800 MHz.

Claims

1. An exciter matching circuit for an input to a power amplifier of a dual band constant envelope modulation communication device selectively operable in a first frequency band and a second frequency band comprising:

a first transmission line, coupled between an input node and a voltage source;

a first capacitor, coupled between the voltage source and a second transmission line;

a second capacitor, coupled between the second transmission line and ground; and

a third transmission line coupled between the second transmission line and the power amplifier,

wherein the first transmission line and the first capacitor transform frequencies in the first frequency band and pass frequencies in the second frequency band, and the second transmission line, the second capacitor, and the third transmission line transform frequencies in the second frequency band and pass frequencies in the first frequency band.

2. An exciter matching circuit according to claim 1 further comprising:

a transistor, having a transistor output coupled to the input node.

3. An exciter matching circuit according to claim 2 wherein the transistor is a bipolar junction transistor and the transistor output is a collector of the bipolar junction transistor.

4. An exciter matching circuit according to claim 1 further comprising:

a resistor, coupled between the input node and the voltage source; and

a third capacitor, coupled between the voltage source and ground.

5. A dual band transmitter, having a power amplifier with power amplifier input impedances and power amplifier output impedances for power efficient operation in a saturated mode at either a first frequency band or a second frequency band, comprising:

an exciter matching circuit, coupled to an input of the power amplifier, for selectively matching an output impedance of the exciter matching circuit in either the first frequency band or the second frequency band to the power amplifier input impedances.

6. A dual band transmitter according to claim 5 wherein the exciter matching circuit comprises:

a first transmission line, coupled between an input node and a voltage source;

a first capacitor, coupled between the voltage source and a second transmission line;

a second capacitor, coupled between the second transmission line and ground; and

a third transmission line coupled between the second transmission line and the power amplifier,

wherein the first transmission line and the first capacitor transform frequencies in the first frequency band and pass frequencies in the second frequency band, and the second transmission line, the second capacitor, and the third transmission line transform frequencies in the second frequency band and pass frequencies in the first frequency band.

7. A dual band transmitter according to claim 6 wherein the exciter matching circuit further comprises:

a transistor, having a transistor output coupled to the input node.

8. A dual band transmitter according to claim 7 wherein the transistor is a bipolar junction transistor and the transistor output is a collector of the bipolar junction transistor.

9. A dual band transmitter according to claim 6 wherein the exciter matching circuit further comprises:

a resistor, coupled between the input node and the voltage source; and

a third capacitor, coupled between the voltage source and ground.